Top seed Halep took no prisoners against Williams, blitzing the 38-year-old American 6-2, 6-2 in just 71 minutes to reach the quarter-finals.

World number one Simona Halep crushed seven-time Grand Slam winner Venus Williams in straight sets on Thursday at the WTA Montreal event just hours after a delivering a marathon three-hour victory over Anastasia Pavlyuchenkova. Top seed Halep took no prisoners against Williams, blitzing the 38-year-old American 6-2, 6-2 in just 71 minutes to reach the quarter-finals. Halep's match against Pavlyuchenkova was originally scheduled for Wednesday night but heavy rains forced organizers to postpone it until Thursday morning.

The Romanian needed three grueling sets to oust the world No. 28 Russian but had a much easier time against veteran Williams who has yet to win a title in 2018.

Williams has struggled with her form this year and hasn't won a Grand Slam title since Wimbledon in 2008 when she beat sister Serena in the final.

"It's never easy to play either of the Williams sisters, and even though she was struggling, I knew I had to be focused on every ball, and stay focused until the end," Halep said.

"She wasn't feeling great on the court and it definitely wasn't her best day. And I'm happy to be the quarter-finals now."

The reigning French Open champion started quickly, winning the first two games en route to taking the opening set.

She also jumped out to a 3-0 lead in the second set and after a slight lull in the middle, she rebounded to run away with the final four games.

Aryna Sabalenka staged one of the biggest wins of her career, saving three match points en route to a 5-7, 6-2, 7-6 (7/4) upset of second seed Caroline Wozniacki.

The 20-year-old saved three match points at 3-5 in the third set -- winning a backhand rally on the first, acing Wozniacki on the second, and crushing a winner that was set up by a big serve on the third.

"I didn't win any of the match points," Wozniacki said. "I had an opportunity. I didn't get it."

US Open champion Sloane Stephens reached the quarter-finals with a rollercoaster 6-2, 7-5 win over Spain's Carla Suarez Navarro.

Third seed Stephens, building up to the start of the defence of her maiden Grand Slam title in New York later this month, squandered three match points at 5-1 in the second set.

That setback allowed Suarez Navarro to battle back to 5-5 before the American steadied herself to claim a third win in three meetings against the Spaniard after 90 minutes on court.